The CBX5 Knockout CAL-27 Polyclonal Cells product from Ascent Research consists of a CRISPR/Cas9-edited polyclonal knockout cell population featuring targeted disruption of the CBX5 gene within the CAL-27 human cell line. This polyclonal population captures a spectrum of gene-disrupted alleles, offering a heterogeneous loss-of-function model that avoids the clonal selection pressures associated with monoclonal isolates. The product is supplied as a live cell population suitable for immediate expansion and downstream functional assays. The polyclonal nature ensures representation of diverse editing outcomes, facilitating robust phenotypic screening without the bias of single-clone expansion.
The host CAL-27 cell line is derived from a primary human tongue squamous cell carcinoma and exhibits an adherent epithelial morphology. As a widely characterized model of head and neck squamous cell carcinoma (HNSCC), CAL-27 cells harbor a mutant p53 tumor suppressor, reflecting the common TP53 alterations in this malignancy. This genetic background makes the line particularly pertinent for dissecting tumor suppressor pathways and the interplay between epigenetic regulation and cancer progression. CAL-27 cells are routinely employed in oral cancer research to investigate mechanisms of invasion, drug resistance, and gene expression dysregulation.
The CBX5 gene encodes heterochromatin protein 1 alpha (HP1??), which binds histone H3 trimethylated at lysine 9 (H3K9me3) to nucleate heterochromatin formation. HP1?? interacts with SUV39H1, the methyltransferase that deposits H3K9me3, and with Lamin B receptor, HP1??, and HP1?? to maintain repressive chromatin domains. Its activity is regulated by upstream factors including E2F1, p53, Aurora B kinase, and ATM/ATR kinases. Downstream, HP1?? represses transcription of cell cycle genes such as cyclin A and E2F targets, promotes senescence-associated heterochromatin foci, and silences LINE-1 retrotransposons, thereby preserving genome stability.
Disruption of CBX5 in CAL-27 cells compromises heterochromatin integrity, leading to derepression of cell cycle genes and abrogation of senescence programs. In the context of mutant p53, HP1?? loss can exacerbate genomic instability and alter DNA damage response (DDR) signaling, making this model particularly relevant for HNSCC research where both pathways are frequently deregulated. The knockout allows dissection of HP1????s role in sustaining the senescent phenotype and suppressing tumorigenesis, and provides a platform to study synthetic lethal interactions that may arise from combined p53 and HP1?? deficiency.
Applications include Western blotting for HP1??, ChIP-qPCR for H3K9me3 enrichment, and immunofluorescence to visualize heterochromatin foci. Senescence-associated ??-galactosidase assays, cell proliferation analyses, and ??H2AX immunostaining enable functional characterization of DNA damage and senescence pathways. RNA-seq can reveal transcriptomic changes upon heterochromatin disruption. These assays facilitate studies of epigenetic dysregulation, senescence bypass, and drug screening in head and neck cancer. For further information, please contact Ascent Research.
